Speciation and Phylogeography
Zack E. Murrell
Associate Professor
Ph.D., Duke University
Postdoctoral, University of Arizona and Harvard University
The Southern Appalachian Mountains have floristic connections to eastern Asia, the mountains of Mexico, and the Pacific Northwest that provide a ready-made experiment in evolution. My research on the phylogeny of dogwoods (Cornus) has used this disjunct distribution pattern to ask various questions about how this group evolved. This work has included analyses at the species level, where I have examined patterns of hybridization and speciation. I am currently examining dogwoods in Asia and the Americas, with a hope of identifying disjunct species pairs for a broader evolutionary analysis.
The distribution of plants within the Southern Appalachians provides another rich research opportunity, and much of my current research is on species genetic structure and speciation in several groups of plants in this region. My lab has examined the genetic structure of the imperiled Virginia Spiraea, and we have used this genetic structure to test hypotheses concerning past plant migrations and regions of refugia during the climatic changes over the past 1-2 million years. This phylogeographic study will be expanded over the next several years to complete a more fine-grained analysis of the genetics of the Virginia Spiraea and to begin similar analyses of other plants. We have examined species relationships within the wild gingers (Hexastylis/Asarum), and have used the patterns of variation seen in this group to generate hypotheses concerning mechanisms of speciation. The work with Spiraea and the wild gingers involves comparisons of morphology and micromorphology, sequence data (Internal Transcribed Spacer region) and RAPD (Randomly Amplified Polymorphic DNA) and allozyme data. We use multiple datasets to compare and contrast molecular and morphological variation as we examine divergences in time and space of populations and species.
The most recent addition to my research interests has been an examination of species that are restricted to the high elevation peaks in the Blue Ridge Mountains. One project on Grandfather Mountain involves an attempt to restore several imperiled species in a rocky ridgetop heath community. A second project is an examination of changes in the flora of Roan Mountain. Both of these studies involve monitoring of imperiled plants, examination of the genetics of imperiled plants, and development of management plans to assist in the recovery and maintenance of these unique high elevation communities.
Hypothesis of relationships in the
genus Cornus (the dogwoods) based
upon morphological, biochemical and anatomical characters.
Selected Publications
Murrell, Z.E. (1994) Dwarf dogwoods: intermediacy and the morphological landscape. Systematic Botany 19: 539-556.
Murrell, Z.E. (1996) Cornus in South and Central America: A new subgeneric classification. Systematic Botany 21(3): 273-288.
Hardin, J.W., and Murrell, Z.E. (1997) Leaf surface structures and evolutionary relationships in the genus Cornus. Journal of the Torrey Botanical Society 124: 124-139.
Murrell, Z.E. (1999) What is the function of an herbarium in a Department of Biology at colleges and comprehensive universities? ASB Bulletin.45(4):194-199.
Anders, C.M., and Murrell, Z.E. (2001) Morphological, molecular, and biogeographical variation within the imperiled Virginia Spiraea. Castanea 66:24-41. |
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